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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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10th Feb 2021, 12:47 pm | #21 |
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Re: Pye M78F questions
Hi Steve.
If you look at the bottom of the page linked it discusses the value of R4 you probably won't need to make it lower for the reduced voltage the object is to get the input to the regulator circuit to be around 6V on load. A lot of people like to run these valve closer to 1.2V to increase their life when being used from a mains supply. Michael Watterson, (Golborne) has written extensively on this subject (Neon Indicator). Cheers Mike T
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10th Feb 2021, 1:16 pm | #22 | |
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Re: Pye M78F questions
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10th Feb 2021, 1:37 pm | #23 | |
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Re: Pye M78F questions
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10th Feb 2021, 2:37 pm | #24 | ||
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Re: Pye M78F questions
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10th Feb 2021, 3:58 pm | #25 |
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Re: Pye M78F questions
Ok, there's probably only one ' pale green/pale cyan' set then. It's just that these two photos made me think that there were a couple of colour variations of the 'green' set. I suppose the giveaway is the distinct 'yellow' colour of the sides of the 'green' set, suggesting an inaccurate (warm) overall colour rendition of that particular photo:
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10th Feb 2021, 4:52 pm | #26 |
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Re: Pye M78F questions
maybe the second radio has been out in the sun too long?
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10th Feb 2021, 5:59 pm | #27 |
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Re: Pye M78F questions
Could just be a difference in white balance between cameras, or colour of lighting. I have an old Raleigh Electronics radio that was black and green, some sort of plastic material, the outside of the case has faded to an almost white colour, I wonder if the same happens to these? What is the case made of?
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10th Feb 2021, 7:07 pm | #28 | |
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Re: Pye M78F questions
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10th Feb 2021, 8:01 pm | #29 | |||
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Re: Pye M78F questions
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11th Feb 2021, 2:28 pm | #30 |
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Re: Pye M78F questions
Having bought a dual output 0-12, 0-12 12VA mains transformer off eBay I've decided to make the power supply. I've already got a suitable box, I guess I'll have most of the C's and R's, and I've just ordered the regulator for a couple of quid for two. Regarding the diodes, there's two different types called for, 1N4001 and 1N4004, surely 1N4004 would do for all of them?
Also, looking at the construction details, the tag strip needs to be 24 tags per side, I can't find any this long?
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11th Feb 2021, 6:14 pm | #31 |
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Re: Pye M78F questions
1N4004 will of course do just fine as would 1N4003, 1N4005, 1N4006 and 1N4007.
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12th Feb 2021, 1:07 pm | #32 |
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Re: Pye M78F questions
For 24/48 way double tag board you can simply buy two of the common 18/36 way ones and mount 6/12 ways cut off the second board alongside the first board.
Or any variation on the theme using odd offcuts of single or double row tags trip to get 24/24. Looking at the layout pics, quite a few tags are unused anyway- with a bit of ingenuity and some split level component mounting a common 18/36 way double tag board could be used on its own.
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12th Feb 2021, 3:39 pm | #33 |
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Re: Pye M78F questions
Does anyone make/sell a pcb for this power supply?
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14th Feb 2021, 6:26 pm | #34 |
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Re: Pye M78F questions
The construction info for the power supply mentions a 'TO220 Insulating Kit for U1'. If I mount the device on tag strip with a 'free standing' heatsink, then if it's not touching anything else then why would it need to be insulated? I assume it's only required in the instance of a metal housing being used as a heatsink? Am I correct? Mine is a plastic housing. Will a strip of thin ali sheet be a good enough heat sink?
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14th Feb 2021, 7:43 pm | #35 |
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Re: Pye M78F questions
Hi Steve should be ok the bigger the better , It all depends on the input volts to output volts , what would be the input voltage . Mick.
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14th Feb 2021, 8:17 pm | #36 |
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Re: Pye M78F questions
Gotcha. Well, as I don't need the full 90v HT output level, my transformer has 2 X 12v outputs, and not 2 X 15v as specified, with the added advantage of requiring less 'drop' on the LT side. So should be less power dissipation.
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14th Feb 2021, 9:03 pm | #37 |
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Re: Pye M78F questions
A TO220 regulator can handle about a watt with no heatsink, A fairly small 10C/W heatsink will up this to about 7-8 Watts. If the heatsink is floating, no insulating kit is required though a smear of heat sink compound or silicone grease is worth adding.
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14th Feb 2021, 11:25 pm | #38 |
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Re: Pye M78F questions
Free standing things with heatsinks don't need insulation if nothing is touching them, but sticking-up things, especially with added mass from heatsinks are fair game for vibration-induced failures. The legs all being in a line, and even worse - flat sections in the same plane, lets TO220 devices 'hinge' until the legs work-harden and fatigue.
David
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15th Feb 2021, 9:07 am | #39 |
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Re: Pye M78F questions
Point taken David. I mean, this isn't going to get much day to day use, it's just basically to enable me to restore the Pye and subsequently given it a run out. But maybe I will tether the heatsink to the plastic case somehow - a spacer and a bolt.
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20th Feb 2021, 7:33 pm | #40 |
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Re: Pye M78F questions
A quick update, I'm about halfway through building the power supply. I'll post some pics soon.
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